1. Field Of The Invention
This invention relates to safety pressure relief devices having reverse buckling discs, and more particularly, to a relief device with a disc having a conical central portion.
2. Description Of The Prior Art
Rupture discs have been used for many years to provide safety pressure relief for pressure vessels or pressurized systems. A problem with early rupture discs was fragmentation of the disc which required cleaning of the fragments of the rupture disc from downstream portions of the system. As a result, discs adapted to rupture without fragmentation were desihned. For relatively high pressure applications, knife blades were necessary to open the thicker rupture discs required. One such apparatus is disclosed in U.S. Pat. No. 3,294,277 to Wood, assigned to the assignee of the present invention. A problem with this type of system is that the knife blade assemblies are costly.
An apparatus providing rupture of a disc without fragmentation at relatively high pressures and without the need of knife blades is disclosed in U.S. Pat. No. 3,484,817 to Wood, also assigned to the assignee of the present invention. This apparatus uses a rupture disc with an annular flat flange and a concave-convex center portion which is positioned between two support members. The concave side of the rupture disc is directed toward the outlet support member. Scoring is privided on the concave-convex center portion for providing lines of weakness thereon. When the inlet pressure exerted on the convex side of the disc reaches a predetermined design level, the elastic stability of the disc becomes unstable causing it to reverse buckle. Upon reversal, the disc will tear along the scoring due to the tensible force exerted on it as a result of the reversing process. The disc thus opens, and, due to the fact that the tearing of the disc occurs along the scoring, no fragmentation occurs.
One limitation to the concave-convex disc shown in U.S. Pat. No. 3,484,817 is that it is not well adapted for relatively low pressures. The relief device of the present invention utilizing a disc having a conical center portion provides a disc which will rupture at relatively low predetermined pressures and still have no fragmentation.